Process for the preparation of specific geometric olefin isomers



United States Patent 2,994,727 PROCESS FOR THE PREPARATION OF SPECIFICGEOMETRIC OLEFIN ISOMERS Herbert R. Appell, North Riverside, and ErwinE.

Meisinger, Elmhurst, lll., ass'gnors, by mesne amignments, to UniversalOil Products Company, Des Plaines, 11]., a corporation of Delaware NoDrawing. Filed Mar. 24, 1958, Ser. No. 723,147 7 Claims. (Cl.260-'683.2)

This invention relates to a process for the preparation of specificgeometric olefin isomers, and more particularly relates to a process forshifting the double bond in an alpha-olefin containing more than threecarbon atoms to a more centrally located position in said olefin andsimultaneously therewith producing one geometric olefin isomer inquantities larger than predicted by equilibrium values. Still morespecifically, this invention relates to a process for the conversion ofl-butene to a mixture of cisand trans-Z-butene in which the ratio of cisto trans isomers is greater than the equilibrium value. Still morespecifically, this invention relates to a process for the separation ofisobutylene from a four carbon atom olefin hydrocarbon fraction.

The recent introduction of automobile engines of high compression ratioshas led to the need for the utilization of processes in the petroleumrefining industry for the production of extremely high antiknockhydrocarbons as fuels. One process for the production of such highantiknocking hydrocarbons is the catalytic alkylation of isoparafiinswith olefins. 'In this alkylation process various catalytic agents havebeen suggested including concentrated sulfuric acid and liquid hydrogenfluoride. With these catalytic agents, for example, the alkylation ofisobutane with four carbon atom olefin fractions or streams has beenpracticed commercially on a wide scale. There has been a general feelingin the practice of these alkylation processes, however, that utilizationof 2-butene as the primary olefinic hydrocarbon results in theproduction of higher octane number alkylate product than does theutilization of l-butene. higher and higher octane number motor fuels hasincreased, the necessity for the development and utilization of aprocess for the conversion of l-butene to Z-butene has widened. Variousprocesses for such double bond shifting have been suggested in the priorart. However, in the main, these processes have been relatively hightemperature ones in which the shifting of the double bond has beenlimited by equilibrium considerations. Furthermore, these four carbonatom olefin hydrocarbon fractions or streams usually contain substantialquantities of isobutylene in addition to l-butene and 2-butene. In thesehigher temperature double bond shifting processes suggested in the priorart polymerization of the isobutylene in these four carbon atom olefinhydrocarbon streams or fractions usually takes place concurrently withthe double bond shifting reaction. This occurs because isoolefinspolymerize more readily than do n-olefins. In addition, this isobutylenepolymerization is not simple self polymerization but usually involvessome 'of the other olefinic hydrocarbons present in so-called crosspolymerization. To avoid this difficulty, the prior art suggestsselective removal of isobutylene from these streams by cold acidtreatment followed by double bond shifting. It has now been discoveredthat this two step process is no longer necessary and can be replaced bya single step process by the utilization of the process of the presentinvention. It is an object of the present invention to provide a processwhich can be utilized at relatively low temperatures, in liquid or vaporphase as may be desired, and in a continuous manner if so desired, toobtain conversion of alpha-olefins to a mixture of cis and As the demandfor' trans olefins in which the double bond is more centrally locatedand in which the ratio of cis to trans isomers is greater than theequilibrium value, and without concurrent isoolefin polymerization orcross polymerization taking place. In this manner the degree ofbranching of the product from catalytic alkylation of isoparafiins withthese olefins is increased since alpha-olefins are eliminated from theolefin feed stock to the catalytic alkylation process. This increasedbranching of the product from catalytic alkylation, as is well known inthe prior art, results in increased octane number of the alkylateproduct.

Furthermore, the process of the present invention has additional utilityresulting from the ability to shift the double bond in alpha-olefins toa more centrally located position without concurrent isoolefinpolymerization. This can perhaps be best understood from the most simpleillustration thereof. The respective boiling points of the four carbonatom olefin hydrocarbons are presented in the following table:

TABLE I Boiling points of four carbon atom olefins From this table it isreadily observed that isobutylene cannot be satisfactorily fractionatedfrom a mixture of four carbon atom olefins since its boiling point of-6.9 C. is only 0.6 C. difierent from the boiling point of l butene.Conversion of the l-butene to 2-butene without isobutylenepolymerization leads to a mixture of isobutylene and 2-butene which canbe separated by fractionation due to the difference in boiling point ofalmost 8 C. Furthermore, if the ratio of cis-2-butene can be increasedto greater than that of the equilibrium value, this further enhances theutility of the separation process since cis-Z-butene has a boiling point10.6 C. above the boiling point of isobutylene. Isobutylene is in widedemand in the chemical industry, particularly for the introduction oftertiary butyl radicals into aromatic compounds -by the alkylationprocess. Since it is obvious from the above table that isobutylenecannot be separated by fractionation from other four carbon atomolefins, it is now prepared for such uses by selective polymerizationfrom such mixtures, fractionation of the polymer and depolymerization.The process of the present invention provides a means by whichisobutylene can be directly separated from four carbon atom olefinhydrocarbon streams or fractions by a simple one step conversion processfollowed by fractionation. Furthermore, this fractionation which resultsin the production of an overhead isobutylene product, also results inthe production of a bottoms Z-butene product which is a particularlydesirable four carbon atom olefin for use for the alkylation ofisobutane.

One embodiment of this invention relates to a process for preparing acis and trans olefin mixture in which the ratio of cis to trans isomersis greater than the equilibrium value which comprises passing an olefinof the following structure.

R R H in which R is selected from alkyl and hydrogen and at least one Ris hydrogen, and R is alkyl, over a deactivated catalyst comprising analkali metal disposed on a support at a temperature within the range offrom about the range of from about to about 100 C., and reactionsincluding some hydrocarbon conversion reactions,

0 to about 100 C., and recovering a mixture of cis and trans olefinsfrom the product.

Another embodiment of this invention relatesto aprocess for preparing acis and trans olefin mixture in which the ratio of cis is to transisomers is greater than the equilibrium value which comprises passing analphaolefin of the following structure in which the R is an alkyl groupover a deactivated catalyst comprising an alkali metal disposed on aprecalcined high surface area support at a temperature'within covering amixture of cis and trans olefins from the product.

A more specific embodiment of this invention relates to a process forpreparing a cisand trans-2-butene mixture in which the ratio of cis totrans isomers is greater than the equilibrium value which comprisespassing 1- butene over a deactivated catalyst comprising sodium disposedon a precalcined high surface area alumina sup- 'port at a temperaturewithin the range of from about 0 to about 100 C., and recovering amixture of cisand trans-:Z-butene from the product.

A specific embodiment of this invention relates to a process forpreparing a cisand trans-Z-butene mixture in which the ratio of cis totrans isomers is greater than the equilibrium value which comprisespassing l-butene over a deactivated catalyst comprising sodiumdisposedon a precalcined high surface area alumina support at a temperaturewithin the range of from about 0 to about -;100 C., said deactivationhaving been accomplished by prior use of the catalyst in hydrocarbonconversion re-' actions, and recovering a mixture of cisandtrans-2-butene from the product. I

Another specific embodiment of the present invention relates to aprocess for the separation of isobutylene from a four carbon atom olefinfraction which comprises passing said fraction at a temperature withinthe range of from about 0 to about 100 C. over a hydrocarbon conversionreaction deactivated catalyst comprising so- .dium disposed on aprecalcined high surface area alumina support, passing eflluents fromsaid reaction to a frac-' tionation zone, and recovering isobutylenefrom the overhead and 2-butene from the bottoms thereof. a

In the last few years the prior art has disclosed the utilization ofalkali metals as catalysts for various reand more specifically olefinisomerization reactions. This prior art, however, discloses minimumoperable temperatures for these hydrocarbon conversion reactionsincluding olefin isomerization reactions in the neighborhood of about150 C. In some instances, the use of extremely high pressures such asover 100 atmospheres have been disclosed as necessary. Attempts toovercome the necessity for such high pressure has led to the discoveryof the use of certain so-called promoters for these alkali metals.However, while the use of such promoters has resulted in the discoverythat lower pressures jare operable, the use of operating temperatures inthe order of about 150 C. or higher has still been considered necessary.It has recently been discovered that these operating temperatures can besubstantially lowered by the simple expedient of disposing the alkalimetal catalyst on a support, and that the resultant catalyst-iseffective for the shifting of double bonds in olefins at relativelymoderate pressures in the absence of any added catalyst promoter. Thisdiscovery is important not only because of the economies in necessaryequipment which may be achieved during the utilization of the process,but also because of equilibrium considerations. For-example, utilizing amixture of four carbon atomolefins, at 277 C. a conversion of l-buteneto Z-butene of 84% is .inreaction zones and which lend themselves toadoption can increase this theoretical conversion to greater than of2-butene. As set forth hereinabove, such an increase in 2-butene contentin a four carbon atom olefin stream utilized for reaction with anisoparaflin to produce high octane number alkylate is extremelyimportant from the octane number standpoint of the alkylate.Furthermore, alkali metals disposed on supports result incataly'ticagents which can be utilized as fixed beds in processes of theso-called continuous fixedbed type which areextremely desirableforadoption'in commercial scale processes. These supported alkali metalcatalytic agents, however, all suffer from one inherent disadvantage.-When properly disposed on a suitable support, these catalyticagents arenot only active for desired reactions such as the shifting of a doublebond in an olefin hydrocarbon but they also cause polymerization ofissoolefins. It has been discovered that proper deactivation of thesecatalytic agents results in their having selective activity. In otherwords, they can be utilized for the preparation of cis and trans olefinmixtures in which the ratio of cis to trans isomers is greater than theequilibrium value, they can be utilized for the conversion ofalpha-olefins to such cis and trans olefin isomer mixtures, and theseconversions can be carried out without simultaneous isoolefinpolymerization. The means for proper deactivation of these catalystswill be described in detail hereinafter.

When processing alpha-olefins over deactivated catalysts comprisingalkali metals disposed on a support in accordance with the process ofthis invention, an unusual product distribution is obtained. Not onlydoes the double bond in the alpha-olefin shift to a more centrallylocated position in the hydrocarbon but the geometry of the productsshows that this shift has been accomplished to give a yield of cisisomer in larger amounts than would be predicted by the equilibriumvalues for the distribution of such products. A readily observed exampleof this specific type of reaction is found in the conversion of l-buteneto a mixture of cisand trans-2- butene in the presence of thesecatalysts and at a reaction temperature of from about 0 to about C. Thisconversion is illustrated further by the following equation:

.The equilibrium data for this reaction are found in an articlebyKilpatrick, J. E., et al., Journal of Research National Burea ofStandards, 36, 559 (1946). These .datashow that at 0 C. the ratio of cisto trans isomers at equilibrium is 0.125 and that the conversion ofl-butene to 2-butene at this temperature is 94.7%. At 100 C. the ratioof cis to trans isomers goes up to 0.458 and-the conversion of 1- toZ-bu-tene at this temperature is 91.7%. -At any selected temperaturebetween 0 and 100 C., the theoretical equilibrium quantities of cisand:trans-2-butene can be found from the above refer- :ence." From thesevalues the ratiofof cis to trans isomers can be calculated and will fallbetween 0.125 and 0.458 as lower and upper limits, respectively. Then byutilization of the process of the present invention, it has g.unexpectedly been found that when converting l-butene to 2-butene theratio of isomers is higher than would be expected based upon theseequilibrium values. For example, at 27 C. the equilibrium cis to transratio is about 0.33. By this process ratios greater than one and as highas 4:1 or higher have been found in the products. Such stereospecificactivity of any catalyst is rare and has not been noted in any catalyticsystem for double bond shifting prior to the present discovery thereof.Not only is the process of the present invention applicable to the abovedescribed system but the abnormal cis to trans ratio of olefin isomersis also obtained when processing other alpha-olefins includingl-pentene, l-hexene, l-heptene, l-octene, l-nonene, l-decene,l-undecene, l-dodecene, l-tn'decene, l-tetradecene, l-pentadecene, etc.Some alpha-olefins inherently cannot form cis and trans isomers becauseof their original structure. Thus, 2-methyl-l-pentene cannot form cisand trans products upon double bond shifting. Therefore, this limitationmeans that each of the carbon atoms which form the double bond in thealpha-olefin must originally have attached thereto at least one hydrogenatom. The alpha carbon atom of the alpha-olefin may have attachedthereto either one or two hydrogen atoms. The beta carbon atom of thealpha-olefin must have attached thereto one and only one hydrogen atom.In accordance with this limitation, alpha-olefins which also may beutilized include 4-methyl-l-pentene, 4-methyl-l-hexene,S-methyl-l-hexene, 4-methyl-l-heptene, S-methyl-l-heptene,G-methyl-lheptene, 4-methyl-l-octene, S-methyl-l-octene,6-methyll-octene, 7-methyl- 'l-octene, etc. Further examples of operableolefins are readily apparent to one skilled in the art.

The olefinic hydrocarbons which are utilized in the process of thisinvention all contain more than three carbon atoms and may be derivedfrom various sources. As pointed out hereinabove, the process of thepresent invention is particularly suited for or adapted to theconversion of l-butene to Z-butene. The l-butene may be charged to theprocess of this invention in pure form or in admixture with otherhydrocarbons including any or all of Z-butene, isobutylene, normalbutane, isobutane, etc. By proper balance of the isobutane content ofsuch a mixture, it will be recognized that the mixture may be a typicalalkylation feed stock. Thus, the process of the present invention may beutilized for the conversion of the l-butene content in an alkylationfeed stock to 2-butene prior to utilization of the feed stock in thealkylation reaction and without danger of isoolefin polymerization, forexample, isobutylene polymerization. The process of the presentinvention can likewise be utilized for shifting the double bond inl-pentene or in Z-methyl-lbutene or 3-methyl-1-butene to producepentenes in which the double bond is in a more centrally locatedposition. When utilized with these isoamylenes, cis and trans productsare obviously not produced since such are not possible from thesestarting materials. Likewise, hexenes such as l-hexene can be convertedto a mixture of cisand trans-Z-hexene in which the ratio of cis to transisomers is greater than equilibrium value. A similar double bond shiftin Z-hexene to 3-hexene also results in a mixture of cis to transisomers in which the ratio is greater than equilibrium value. The doublebond shifting reaction of the present invention of l-olefins oralphaolefins to olefins in which the double bond is in a more centrallylocated position is readily adaptable to any feed stocks as disclosed inthe prior art, and without the danger of isoolefin polymerization which,as set forth hereinabove, occurs in prior art processes. While thepresent invention is discussed in detail in relation to the shifting ofthe double bond in l-butene to produce cisand trans-Z-butene in a cis totrans isomer ratio greater than the equilibrium value, this discussionis introduced merely for the purpose of convenience and with notintention of unduly limiting the olefinic hydrocarbons which can beconverted in accordance with this process.

As set forth hereinabove the process for shifting the double bond in theolefinic hydrocarbon to a more centrally located position in theolefinic hydrocarbon and to produce a mixture of cis and trans olefinsin which the ratio of cis to trans isomers is greater than equilibriumvalue is effected in the presence of a deactivated catalyst comprisingan alkali metal disposed on a support. The methods for, means of, anddescription of the deactivation of these catalysts will be set forthhereinafter. The alkali metal catalysts which, after deactivation, areutilizable in the process are selected fi'om the group consisting oflithium, sodium, potassium, rubidium, and cesium, or mixtures thereof.Of these alkali metals, the more plentiful and less expensive sodium andpotassium are preferred, either alone or in admixture with one another.These alkali metals are disposed on a support in a quantity ranging fromabout 2% to about 30% by weight based on the support. Not every supportcan be utilized as a satisfactory one for disposal of an alkali metalthereon. As is well known, the alkali metals react violently with waterand thus care must be taken to utilize a support which is relatively orsubstantially free from water. In mose cases this freedom from water ofthe support is achieved by precalcination of the support. Thisprecalcination is usually carried out at relatively high temperature inthe range of from about 400 to about 700 C. and for a time sufiicient toeffect substantial removal of adsorbed or combined water from thesupport. These times will vary depending upon the support, and dependingupon whether the Water is in a combined or in merely a physicallyadsorbed form. In addition to the necessity for freedom from water, thesupport is additionally characterized in the necessity for having a highsurface area. By the term high surface area is meant a surface areameasured by adsorption techniques within the range of from about 25 toabout 500 or more square meters per gram. For example, it has been foundthat certain low surface area supports such as alpha-alumina which isobviously free from combined Water and which has been freed fromadsorbed water is not a satisfactory support for the alkali metals inthe preparation of catalysts for use in the process of this invention.Alpha-alumina is usually characterized by a surface area ranging fromabout 10 to about 25 square meters per gram. In contrast, gammaaluminawhich has a surface area ranging from about to about 300 square metersper gram, and which has been freed from adsorbed Water, and whichcontains no combined water, is a satisfactory support. Celite, anaturally occurring mineral, after precalcination, is not a satisfactorysupport. Celite has a surface area of from about 2 to about 10 squaremeters per gram. Likewise, alkali metal dispersions on sand or on otherlow surface area silicas are not satisfactory catalysts in this process.In addition, aluminas which contain combined water but which haverelatively high surface areas are also not satisfactory supports. Suchaluminas include dried aluminum monohydrates which have not beensufficiently calcined to remove combined water and to formgamma-alumina. These alumina hydrates may have surface areas rangingfrom about 50 to about 200 square meters per gram but because theycontain combined water are not satisfactory supports. Particularlypreferred supports for use in the process of this invention include highsurface area crystalline alumina modifications such as gamma-alumina andtheta-alumina, high surface area silica, charcoals, magnesia,silica-alumina, silica-alumina-magnesia, etc. However, as is obviousfrom the above discussion, the limitation on the use of any particularsupport is one of freedom from combined or adsorbed water in combinationwith the desired surface area of the selected support.

The alkali metal may be disposed on a support in any manner. One mannerwhich has been found suitable is vaporization of the alkali metal andpassage of the .and in impregnating 'a selected support with sodium itis preferred to carry out the impregnation or disposal of the sodiumthereon at temperatures in the order of from about 100 to about 150 C.This can be accomplished, for example, by melting sodium and by droppingthe sodium on the support or by the passage of a stream of an inert gassuch as nitrogen or argon through the molten sodium and over a bed ofthe selected support disposed in a separate zone maintained at thedesired temperature with cooling or heating means connected therewith.Potassium melts at about 62 C. and thus the impregnation of a selectedsupport with potassium can be carried out at even :lower temperatures.Potassium disposed on one of the above mentioned supports appears to bea more active catalyst for the reactions disclosed herein than doessodium and this difference in activity may be due to the lowertemperature which can be used in the disposal of potassium on thesupport. Supported lithium catalysts appear to be less active thansodium or potassium catalysts and this may be a reflection of the highermelting point of lithium, 186 C., and the higher temperatures which mustoccur on contact of the lithium with the support. Furthermore, disposalof the selected alkali metal on the support must be carried out in amanner so that the high surface of the support in combination with thealkali metal is not destroyed by incorporation of excess quantities ofthe alkali metal therein. In other words, the pores and passageways ofthe support can be filled and blocked by the addition of excessquantities of alkali metal. This is obviously undesirable and supportedalkali metal catalysts containing excess alkali metal are likewiseinactive in the process.

After prepartion of the initial alkali metal disposed on a support, thecatalytic activity of the composite is lowered to eliminate isoolefinpolymerization activity. This deactivation may be accomplished invarious manners and by various means. One method for deactivation is bythe passage of dry air or dry oxygen over the composite. Apparently somepolymerization activity of the composite is decreased or destroyed byoxidation in this manner-with the resultant production of a catalyticagent active for double bond isomerization and for the production of cisto trans isomers in a ratio greater than equilibrium value. The exactmanner in which the air or oxygen deactiv-ates the composite is notknown. Another means or method for deactivation of the polymerizationactivity of the composites is to utilize them for a hydrocarbonconversion reaction until their activity for such reaction declines, andthen to use them in the process of the present invention. For example,utilization of the catalyst composite of an alkali metal disposed on asupport for the polymerization of isoolefins until isoolefin conversiondecreases, and then utilization of the thus deactivated composite in theprocess of the present invention results in satisfactory catalystactivity in this process. The catalytic agents comprising alkali metalsdisposed on supports may also be deactivated by utilization in otherhydrocarbon conversion reactions including paraflin isomerization, sidechain alkylation, isoparaffin alkylation, cracking, etc. In someinstances, mere passage of a hydrocarbon such as isobutane over thealloying with non-catalytic metals. These non-catalytic metals may bedivided into three classes, namely, those which form solutions withmetals, those in which alkali metals are partially soluble, and those inwhich alkali metals are slightly soluble or relatively insoluble.Exampes of the non-catalytic metals in which the alkali metals aresoluble include antimony, tin, arsenic, bismuth, cadmium, gold, lead,mercury, and silver. Zinc is an example of a metal in which the alkalimetals are partially soluble, and examples of metals in which the alkalimetals are slightly soluble include cerium, gallium, germanium, indium,platinum, palladium, and nickel. The alloys are usually prepared bycombining an equimolecular quantity of the alkali metal andnon-catalytic metal to be alloyed therewith, although greater or smalleramounts of the noncatalytic metal may be utilized. Of the abovementioned non-catalytic metals which may be alloyed with alkali metals,those in which the alkali metals are soluble are definitely prefer-red.Due to the solubilizing property of these particular non-catalyticmetals, liquid melts with alkali metals can be readily prepared andutilized for or as a means of disposal of the alkali metal on thesupport.

For example, equimolecular proportions of sodium and arsenic form asolution which can readily be added to a selected support such as aprecalcined high surface area alumina support. Likewise, an alloy ofsodium and mercury may be utilized as the means for disposing the alkalimetal on the preselected support. Due to the varying molecular weightsof the respective non-catalytic alloying metals the actual quantity ofalloying metal in the final deactivated catalyst composites may varyover a relatively wide range of from about one to about 40% by weightbased on the support.

The catalytic composite utilized in the process of the present inventionmay be deactivated in a further manner, that is, by utilization underprocessing conditions at which conversion to equilibrium mixtures is notobtained. As set forth hereinabove, one of the features of the processof the present invention is that the catalytic composites may beutilized at relatively low temperature, that is, from about 0 to aboutC. With the freshly prepared composites comprising alkali metalsdisposed on a support conversion of alpha-olefins to equilibriummixtures of cis and trans olefins in which the double bond is morecentrally located are readily obtained. These conversions to equilibriummixtures are attained at relatively low hourly liquid space velocitiesbased on the olefin in the range of from about 0.1 to about 2. As thehourly liquid space velocity is increased to 4 or 8 or 16 or more, thetotal conversion tends to drop oif somewhat, but it is observed that theproducts produced no longer contain equilibrium mixtures ofv cis andtrans isomers but the mixtures contain the cis isomer in quantitiesgreater than would have been predicted by equilibrium, and the transisomer in quantities less than would have been predicted by equilibrium.From this type of a product distribution it is obvious that the cis totrans ratio will be greater than that which can be calculated from theequilibrium quantities of the respective cis and trans isomers at thetemperature utilized for the conversion reaction. Therefore, deactivatedcatalysts, in the sense in which the term deactivated catalyst is usedin this specification and in the appended claims,'-also means a catalystwith which deactivation has been accomplished by utilization of thecatalyst at high hourly liquid space velocity conditions. Thisparticular feature will be illustrated further in connection with the,examples utilizing the conversion reaction of l-butene to a mixture ofcisand trans-Z-butene.

As set forth hereinabove, catalysts of the alkali metal type disposed ona support and deactivated in the manner described may be utilized in theprocess in a manner which enables the process to be carried out atso-called mild operating conditions. As set forth hereinabove, the thusdeactivated catalysts are particularly adapted for use in so-calledfixed bed processes. The doubl bond shifting reaction of the presentinvention to produce a mixture of olefins in which the cis to transratio is greater than equilibrium value can thus be carried out in thepresence of these catalysts at temperatures in the range of from aboutto about 100 C. and at pressures ranging from atmospheric to about 1000pounds per square inch or more. Pressure does not appear to be acritical variable in the process since the conversion reaction may becarried out in either liquid phase or in vapor phase. Thus, the pressureutilized may be selected purely from the most advantageous pressurebased on economic considerations and upon the stability of theparticular olefinic hydrocarbon charged to the process under thenecessary processing conditions. In carrying out the procms of thisinvention in a continuous manner, hourly liquid space velocities basedon the quantity of olefinic hydrocarbon charged may be varied within therelatively wide range of from about 0.1 to about 20 or more. The lowerspace velocities are utilized with what may be considered to bepredeactivated catalysts and the higher space velocities are utilizedwith catalysts which have not been deactivated prior to use but withwhich deactivation is accomplished by use at these higher spacevelocities.

The attainment of the desired shifting of the double bond in an olefinichydrocarbon to a more centrally located position with the production ofcis and trans isomers in a ratio greater than the equilibrium value isaccomplished by the process of the present invention in the absence ofso-called alkali metal catalyst promoters as taught by the prior art.These promoters include organic compounds capable of reacting with aportion of the alkali metal and forming organo metallic compounds insitu during the residence time of the reactants in the reaction zone inthe presence of the alkali metal. Heretofore it has been considerednecessary to utilize such promoters to carry out a process similar tothat of the proc-- ess of the present invention at so-called moderatepressures and temperatures. As set forth above, it has now been foundthat such promoters are not needed and that the process of the presentinvention may be carried out at relatively low pressures andtemperatures by utilization of the deactivated catalysts comprising analkali metal 0.8%. This mixture was charged to the autoclave along with10 grams of sodium metal. After the two hour contacting time, thehydrocarbons were removed from the autoclave, condensed, and analyzedagain. The analysis of the hydrocarbon product in mol percent is asfollows: propane, 0.3%; propylene, 0.2%; normal butane, 0.1%; l-butene,96.9%; cis-Z-butene, 1.3%; and trans-2- butene, 1.2%.

These results show that finely divided metallic sodium is not aneffective catalyst at a temperature of 110 C. for the conversion ofl-butene to Z-butene. While sodium alone is a catalyst for thisconversion at higher temperatures, at higher pressures, and in thepresence of added promoters, it is obvious that it is not an eifectivecatalyst in the temperature range Where equilibrium considerationsresult in the highest yield of 2-butene.

EXAMPLE II The catalyst utilized in this example was prepared by addingsodium to a stirred mass of freshly calcined gamma-alumina in a nitrogenatmosphere, The gamma alumina prior to use was freed from adsorbed andcombined Water by calcination at 650 C. After calcin ation it had asurface area of about 200 square meters per gram. Sulficient moltensodium was dropped onto the stirred alumina mass so that the resultantcomposite of sodium on alumina contained about 16% by weight of sodiumbased on the alumina. During the impregnation of the alurrrina with thesodium, the temperature of the alumina mass stayed between about 150 toabout 170 C.

In several experiments, 100 milliliters of the above sodium dispersed ongamma-alumina was placed as a fixed bed in a reaction tube surrounded byheating means. The same C olefinic hydrocarbon described in Example Iwas then passed over this fixed bed of catalyst at room temperature, at300 p.s.i.g., and at varying hourly liquid space velocities. Prior toeach test period sufiicient prerun periods, for example up to threehours duration, were carried out to insure that the reaction had reachedconstant conversion. The hourly liquid space velocities utilized,maximum temperature attained, and product analyses for five tests atvarying space velocities are presented in the following table:

disposed on a preselected support. This feature of the invention will beillustrated further in the examples.

EXAMPLE I This example is introduced for the purposes of comparison. Inthis example, unsupported sodium was used in an attempt to catalyze theconversion of l-butene to 2-butene. The experiment was carried out at apressure of 350 p.s.i.g., a temperature of 112 C., and for a residencetime of 120 minutes. The experiment was conducted in a one litercapacity turbomixer autoclave which provides a highly eflicient stirringmeans for contacting, and which during the contacting disperses thesodium throughout the reaction vessel in a finely divided form in thereactants.

The hydrocarbon charged to the turbomixer autoclave comprises 300 cc. ofa C fraction having the following analysis in mol percent: propane,0.3%; isobutane, 0.2%; normal butane, 0.1%; l-butene, 98.6%; andZ-butene,

Table II illustrates the fact that sodium disposed on gam ma-alumina isa highly eifective catalyst for the conversion of l-butene to Z-buteneat low temperatures, and at hourly liquid space velocities up to 8,conversions close to the theoretical are obtained. At an hourly liquidspace velocity of 16, and at room temperature, conversion was notcomplete. However, the higher hourly liquid space velocities wereefiective for producing 2-butene isomers such that the ratios weregreater than the equilibrium value. The ratios are apparently Withinexperimental error for the hourly liquid space velocities of 1 and 2.Marked increase in cis to trans ratio is obtained at the hourly liquidspace velocities of 4, 8, and 16. At 16 hourly liquid space velocity thecis to trans ratio of 1.38 is four times greater than the equilibriumratio indicating the stereospecificity of the reaction under theseconditions.

EXAMPLE III In this example, another milliliters of the catalyst,prepared as described in Example H was utilized. How- ,ever, in thisexample the catalyst was treated with air after placement as a fixed bedin the reaction tube. Air'was 'passed over the fixed bed of catalystuntil the evolution of heat due to this treatment ceased.

The same C olefinic hydrocarbon feed stock described in Example I andcomprising mainly l-butene was passed over the fixed bed of air treatedsodium-alumina composite. Conditions utilized included 300 p.s.i.g., amaxi- .mum catalyst temperature of 32 C., and an hourly liq- .u id.space velocity of 2.0. Analysis of the condensable gas product showedthat it contained 6.3% of l-butene, 48.2% of cis-2-butene, and 45.1% oftrans-2-butene. The ratio of cis to trans isomers obtained is 1.07, orabout three times higher than would be expected from the equilibriumratio of 0.33 for this temperature.

EXAMPLE IV The catalyst for this example was prepared by calcining 46grams of gamma-alumina at a temperature of 650 C. to remove combined andadsorbed water. This gammaalumina has a surface area of about 200 squaremeters Per gram. This alumina was placed in a flask and heated to 200 C.in an atmosphere of argon. Then, 8.5 grams of sodium was added. Thefinal catalyst composite contains 15.6% sodium.

The above catalyst, 100 milliliters, was placed as a fixed bed in areaction zone and tested for the conversion of lbutene to 2-butene atroom temperature, a pressure of 300 p.s.i.g., and at an hourly liquidspace velocity of 16.0. The C olefinic hydrocarbon feed stock was thesame as that described hereinabove in Example I. The condensable gasanalysis showed that the product contained 22.4 mol percent l-butene,55.9 mol percent cis-2-butene, 19.1 mol percent tIans-Z-butene, and 2.6mol percent other components. A cis to trans isomer ratio of 2.92 wasobtained in comparison to the theoretical value of 0.33 for thistemperature.

EXAMPLE V Another catalyst was prepared by calcining 46 grams ofgamma-alumina at 650 C. to remove combined and adsorbed water and todevelop a surface area of about 200 square meters per gram. Then, 11.7grams of potassium were added in three gram portions at 6070 C. Thefinal composite was a blue-black color and contained 20.5

by weight of potassium.

In this example, 100 milliliters of the catalyst composite was againdisposed as a fixed bed in a reaction zone. Another sample of the same Colefinic hydrocarbon described in Example I was passed over thiscatalyst at room temperature, 300 p.s.i.g., and at an hourly liquidspace velocity of 16.8. At this space velocity, the product contained9.0 mol percent l-butene, 30.0 mol percent cis-Z-butene, 53.7 molpercent trans-2-butene, and -7.3 mol percent other components. This cisto trans isomer ratio of 0.56 is greater than the equilibrium ratio of0.33 for this temperature.

EXAMPLE VI Another catalyst was prepared utilizing gamma-aluminacalcined for four hours at 500 C. This alumina has a surface area ofabout 225 square meters per gram. After calcination, while hot, thealumina is placed in a flask and a stream of nitrogen passedtherethrough to provide an inert atmosphere. When the temperaturedecreased to less than 100 C. sodium was added so that the finalcomposite contained 12.5% by weight of sodium. This cata; lyst was thenutilized for the polymerization of isobutylene until it becomedeactivated for this reaction. The percent polymer produced had droppedfrom an original 79% based on the isobutylene feed to 28% when thecatalyst was considered to be deactivated.

A sample of this catalyst, 100 milliliters, was placed as a fixed bed ina reaction tube and utilized for the conversion of l-butene to 2-buteneat room temperature, 300

p.s.i.g., and ata space velocity of about 4.- -In one test analysis ofthe condensable gas showed that it contained 29.7 mol percent l-butene,57.9 mol percent cis-Z-butene, 12.3 mol percent trans-Z-butene, and 0.1mol percent other components. In a second test analysis of thecondensable gas showed that the product contained 55.7 mol percent1-butene, 38.3 mol percent cis-2-butene, 5.7 mol percent trans-2-butene,and 0.3 mol percent other components. The ratio 'of-cis to trans isomersfor these test periods was 4.7 and 6.7, respectively, in comparison tothe theoretical ratio of isomers of 0.33.

EXAMPLE VII Another catalyst was prepared rutilizing 45.7 grams ofgamma-alumina which was dried at 500 C. and poured while hot into aflask. Nitrogen was passed through the flask to flush air out of thesystem. Molten sodium in the quantity of 6.5 grams was added in threegram portions. The temperature during this addition was kept below C.This sodium impregnated alumina was disposed as a fixed bed in areaction tube and isobutane passed through the reaction tube for threehours at an hourly liquid space velocity of 8.0.

At the end of this time, the hydrocarbons passed over the sodium-aluminacomposite were switched from isobutane to the same C olefinichydrocarbon feed stock described in Example I. At this point theconditions utilized were 300 p.s.i.g., room temperature, and an hourlyliquid space velocity of 16. The condensable gases in the reaction zoneefliuent were analyzed and contained 54.0 mol percent l-butene, 36.0 molpercent cis-2- butene, 7.9 mol percent trans-2-butene, and 2.1 molpercent other components. The ratio of cis to trans isomers obtained inthis reaction zone eflluent was 4.57 in contrast to the value of 0.33 atequilibrium. This example again illustrates the utilization ofdeactivated catalysts in the process of this invention.

EXAMPLE VIII Another catalyst was prepared utilizing 46 grams ofgamma-alumina which was dried at 500 C. and poured while hot into aflask. Argon was passed through the flask to flush air out of thesystem. A mixture comprising 0.34 gram of mercury and 6.6 grams ofsodium was added to the alumina at about 100 C. The final compositecontained 12.5 sodium alloyed with mercury.

One hundred milliliters of the above composite was placed as a fixed bedin a reaction tube and utilized for the conversion ofi l-butene toZ-butene. Conditions utilized included a pressure of 300 p.s.i.g., roomtemperature, and an hourly liquid space velocity of 16. Analysis of thecondensable gas product showed that it contained 56.2 mol percentl-butene, 33.8 mol percent cis-2-butene, 7.3 mol percent trans-2-butene,and 2.7 mol percent other components. The ratio of cisto trans-2-buteneisomers obtained was 4.63 in contrast to the equilibrium value EXAMPLE1x Another alloy catalyst was prepared containing arsenic and sodium.Here again 46 grams of gamma-alumina previously dried at 500 C. wasutilized. This alumina was placed in a flask which was then flushed withnitrogen. When the aliumina had cooled to a temperature of C., 3.5 gramsof arsenic dissolved in 6.6 grams of sodium was added. The finalcomposite contained 12.3% sodium alloyed with arsenic.

This catalyst in the quantity of 100 milliliters was again placed as afixed bed in a reaction tube and utilized for the conversion of l-buteneto Z-butene. The same C olefinic hydrocarbon feed stock described inExample I was again utilized. The conditions utilized for this exsis ofthe condensable gas therefrom showed that it contained 61.7 mol percentl-butene, 27.8 mol percent cis-2-butene, 6.3 mol percent trans-2-butene,and 4.2 mol percent other components. The ratio of cis to trans isomersobtained during this test was 4.35 in compartison to the equilibriumvalue of 0.33. Here again, the production of a mixture of cis and transisomers in a ratio greater than the equilibrium value is demonstrated bythe utilization of the process of this invention.

We claim as our invention:

1. A process for preparing a cis and trans olefin mixture in which theratio of cis to trans isomers is greater than the equilibrium valuewhich comprises isomerizing an olefinic hydrocarbon feed whose olefincontent consists essentially of at least one olefin of more than threecarbon atoms per molecule and having the following structure:

in which R is selected from alkyl and hydrogen and at least one R ishydrogen, and R is alkyl, in the presence of a deactivated catalystcomprising an alkali metal disposed on a substantially anhydrous supportat a temperature Within the range of from about to about 100 C., saidsupport having a surface area of from about 25 to about 500 squaremeters per gram and said catalyst having had its catalytic activitylowered, prior to use in said process, sufficiently to eliminateisoolefin polymerization activity, and recovering a mixture of cis andtransolefins from the product.

2. The process of claim 1 further characterized in that said feed is ahydrocarbon fraction consisting essentially of C olefinic and parafiinichydrocarbons.

3. A process for preparing a cis and trans olefin mixture in which theratio of cis to trans isomers is greater than the equilibrium valuewhich comprises isomerizing an olefinic hydrocarbon feed whose olefincontent consists essentially of at least one alpha-olefin of thefollowing structure:

in which R is an alkyl group of at least two carbon atoms, in thepresence of a deactivated catalyst comprising an alkali metal disposedon a substantially anh drous support at a temperature within the rangeof from about 0 to about 100 C., said support having a surface area offrom about 25 to about 500 square meters per gram and said catalysthaving had its catalytic activity lowered, prior to use in said process,sufiicient ly to eliminate isoolefin polymerization activity, andrecovering a mixture of cis and trans olefins from the product.

4. A process for preparing a cis and trans olefin mixture in which theratio of cis to trans isomers is greater than the equilibrium valuewhich comprises isomerizing an olefinic hydrocarbon feed whose olefincontent consists essentially of at least one alpha-olefin of thefollowing structure:

in which R is an alkyl group of at least two carbon atoms, in thepresence of a deactivated catalyst comprising an alkali metal disposedon a precalcined alumina support at a temperature within the range offrom about 0 to about C., said support having a surface area of fromabout 25 to about 500 square meters per gram and said catalyst havinghad its catalytic activity lowered, prior to use in said process,sufliciently to eliminate isoolefin polymerization activity, andrecovering a mixture of cis and trans olefins from the product.

5. A process for preparing a cis and trans olefin mixture in which theratio of cis to trans isomers is greater than the equilibrium valuewhich comprises isomerizing an olefinic hydrocarbon feed whose olefincontent consists essentially of at least one alpha-olefin of thefollowing structure:

in which R is an alkyl group of at least two carbon atoms, in thepresence of a deactivated catalyst comprising sodium disposed on aprecalcined alumina support at a temperature within the range of fromabout 0 to about 100 C., said support having a surface area of fromabout 25 to about 500 square meters per gram and said catalyst havinghad its catalytic activity lowered, prior to use in said process,sufiiciently to eliminate isoolefin polymerization activity, andrecovering a mixture of cis and trans olefins from the product.

6. The process of claim 3 further characterized in that saidalpha-olefin is l-butene.

7. The process of claim 5 further characterized in that saidalpha-olefin is l-butene.

References Cited in the file of this patent UNITED STATES PATENTS2,403,439 Ipatiefi et al. July 9, 1946 2,594,343 Pines Apr. 29, 19522,740,820 \Vilson et al Apr. 3, 1956 2,804,489 Pines Aug. 27, 19572,836,633 Esmay et al. May 27, 1958 2,863,923 Bortnick Dec. 9, 19582,887,472 Fotis May 29, 1959 OTHER REFERENCES I.A.C.S. vol. 77, pp. 347and 348, Jan. 20, 1955.

1. A PROCESS FOR PREPARING A CIS AND TRANS OLEFIN MIXTURE IN WHICH THERATIO OF CIS TO TRANS ISOMERS IS GREATER THAN THE QUILIBIRUM VALUE WHICHCOMPRISES ISOMERIZING AN OLEFINIC HYDROCARBON FEED WHOSE OLEFIN CONTENTCONSISTS ESSENTIALLY OF AT LEAST ONE OLEFIN OF MORE THAN THREE CARBONATOMS PER MOLECULE AND HAVING THE FOLLOWING STRUCTURE: